When making an emergency stop, the driver of a vehicle attracts the attention of the drivers of following vehicles by turning on its hazard lamps. Further, there is provided a technique of illuminating a road surface with a display showing a region which is dangerous to enter, thereby providing a warning particularly for two-wheeled vehicles and pedestrians (for example, refer to patent literature 1). Further, there is provided a technique of illuminating a rear road surface with characters of “STOP”, thereby transmitting information also to following vehicles other than the following vehicle just behind the vehicle (for example, refer to patent literature 2).